[yayachiken]

For me this sounds just like the lecturer inserted some casual sexism.

I can say from my own experience at least at my university, that "Altherrenhumor" ("old gentleman humor") like this is still very common in German engineering lectures even today, or at least well into the 2010s.

I would even call such a re-ordering of the genders in the greeting very tame. If you are a woman, you better come to your lectures on time. If you enter the hall half a minute late, the entire hall would whistle at you and cat-call you. Sometimes with support of the lecturer, who would consider it appropriate hazing for "disturbing" the lecture by being late.

At least there started to be at least some sort of push-back by the administration during the years in which I studied, and the really bad stuff only seemed to happen in classes dominated by the mechanical engineers.